Cathode for x-ray tubes.



F. 1-. FARRELLY -& A GREINER.

CATHODE FOR X-RAY TUBES.

APPLICATION FILED. DEC-,ZB. I914.

1 ,275, 5 12.. Patented Aw. 13, 1918.

WITNESSES.-

INVENTORS F 'Ji' 2!: Aiirsszrezq'zi- A TTOR NE Y.

RELLY,

, Gunmen, a sub ect of the Emperor of them.

higher atomic FRANCIS J. FARRELLY AND ALFRED GBJEINEB, 0F HARTFORD, CONll'EGTICUT.

CATHODE FOR X-BJAY TUBES.

Application filed December 28, 1914.

To all w from it may concern:

Be it known that we, FRANCIS J. FAR- a citizen of the United States, and resident of Hartford, county of Hartford, and State of Connecticut, and Angie!) ermany, and resident of Hartford, county of Hartford, invented certain new and useful Improvements in Cathodes for X-Ray Tubes, of which the following is a specification.

This invention relates to an improvement in the manufacture of cathodes for X-ray tubes, the object being to provide an imroved construction which will increase the life of the X-ray tube by eliminating to a large extent the danger of cracking the glass at what is termed the cathode neck. In the drawings Figure 1 is an X-ray tube which may be' assumed to be equipped with a cathode made in accordance with our invention.

. Fig. 2 is a transverse sectional view of the cathode illustrating the invention.

The new cathode is characterized bythe fact that it is formed of two metals of difierent characteristics,

these two metals being united together, or at least having for electrical conduction between a denotes the main body of the cathode, which may be of aluminum, the material now almost universally used for this purpose; and 6 indicates a shell of other material, such a copper or iron, which surrounds and is either shrunk on, plated on, or pinned on to the maiinbody, or properly secured in some other The chief distinguishing characteristic of the two metals making, up the cathode is that one should be of low atomic weight, in order that it may freely give off electrons during the'operation of the tube, and the other of higher atomic weight giving off less electrons. Furthermore, the metal of the weight should preferably be ad acent to the glass wall of the tube. The cs thode rather closely fills the cathode neck, and is customarily located at the point where the cathode neck is joined to the main bulb,

closely a path Specification of Letters Patent.

and the interposition of and State of Connecticut, haveprising a Serial No. 879,263.

this second metal of different characteristics and of greater atomic weight than the main body of the cathode eliminates unusual heating at the cathode neck, and thus reduces to a considerable extent breakage at this point.

The shape of the cathode may not be material, though we prefer to use a cathode like or similar to that illustrated in the patent issued to Henry Green, July 29th, 1913, No. 1,068,426.

lVe claim as our invention:

1. A cathode for use in X-ray tubes cylindrical in shape and formed from two metals of difi'erent characteristics.

2. A cathode for use in X-ray tubes cylindrioal in shape and formed from two metals of different atomic weights.

3. A cylindrical cathode for use in X-ray tubes comprising a main body of aluminum, and a metal of higher atomic weight applied and secured thereto.

4. A. cylindrical cathode for use in X-i'ay tubes comprising a mainbody of aluminum,

higher atomic I and a sleeve of metal of weight secured thereon.

5. A cylindrical cathode for use in X=ray tubes comprising a main body of aluminum, and a metal of higher atomic weight interposed between said main body and the ad jacent wall of the tube and connected with said main body by a path of electrical conduction.

Patented Aug. 13, 1918.

6. The combination in X-ray tubes with i the glass envelop andf anode of usual construction mounted in one-end of said envelop, of a cathode mounted in the other end of said envelop and opei atively p0si-- tioned relative thereto, said cathode comcylindrical body of aluminum, and an inclosing shell formed from a metal of higher atomic Weight mounted thereon and connected therewith by a path of eleo trical conduction.

FRANCIS J FARRELLY. ALFREDGREINER. Witnesses:

' H. E. HART,

A. E. OBRIERZ- 

